The goal of this project is to develop inhalation exposure, tissue burden preparation and analysis methods and histopathology methods to facilitate the NTPs designing of toxicity and carcinogenicity studies of naturally occurring asbestos. There is a need to generate high quality, dose response data on different types of asbestos fibers. However, there are numerous methodological challenges that need to be resolved prior to finalization of the design of these studies. Method development work is currently in progress. Keywords: toxicity, carcinogenicity, asbestos, inhalation, fiber